Statistics show thumbs down?

I just published an article and “liked” it myself. Then I went into the statistics page and saw a thumbs down from another guest user (ip). How is this possible? People can’t down vote posts and wouldn’t it require people to upvote and then downvote? I noticed the downvotes several time. Seems to make no sense.

So is it likely that people are upvoting then directly downvoting or is something broken?